Photochemical coal dissolution. Quarterly technical progress report, July 1--September 30, 1995

Examination of the photochemical extractions of the four Argonne Premium Coal Residues has been under way in a routine manner during this last quarter. An unexpectedly great effort last quarter had been necessary to find extraction solvents and photochemical reagents that were photochemically stable and inert. While it is a rather poor thermal extraction solvent, acetonitrile has proven to be the best solvent the authors have examined. In addition to runs with only the acetonitrile solvent present, experiments were performed with the photochemical reagents, benzophenone and pyridine. Both ketone and pyridine triplet states are well-known for their hydrogen abstraction and electron transfer capabilities. The photochemical reagents were used at concentrations resulting in 50% transmission of the light across the reactor pathlength at 320 nm. Experiments with the quartz cutoff filter remain to be completed at concentrations resulting in 50% transmittance at lower wavelengths. Changes in the transmission of light by the column effluent were monitored continuously and the extraction yield by weight was measured by evaporation of the solvent and subtraction of reagent weight. Thermal extraction yields without light under otherwise identical conditions were measured for comparison. As a check on undesirable effects, such as solvent photochemical degradation, otherwise identical light and dark experiments were also done without the coal on the column